importNode() polyfill for IE8

importNode-polyfill.js

'use strict';

if(!window.DocumentFragment && window.HTMLDocument) {
	window.DocumentFragment = HTMLDocument;
}

if(!document.ELEMENT_NODE) {
	document.ELEMENT_NODE = 1;
	document.ATTRIBUTE_NODE = 2;
	document.TEXT_NODE = 3;
	document.CDATA_SECTION_NODE = 4;
	document.ENTITY_REFERENCE_NODE = 5;
	document.ENTITY_NODE = 6;
	document.PROCESSING_INSTRUCTION_NODE = 7;
	document.COMMENT_NODE = 8;
	document.DOCUMENT_NODE = 9;
	document.DOCUMENT_TYPE_NODE = 10;
	document.DOCUMENT_FRAGMENT_NODE = 11;
	document.NOTATION_NODE = 12;
}

if(!document.createElementNS) {
	document.createElementNS = function(namespaceURI, qualifiedName) {
		return document.createElement(qualifiedName);
	};
}

if(!document.importNode) {
	document.importNode = function(node, deep) {
		var a, i, il;

		switch (node.nodeType) {
			case document.ELEMENT_NODE:
				var newNode = document.createElementNS(node.namespaceURI, node.nodeName);
				if (node.attributes && node.attributes.length > 0) {
					for (i = 0, il = node.attributes.length; i < il; i++) {
						a = node.attributes[i];
						try {
							newNode.setAttributeNS(a.namespaceURI, a.nodeName, node.getAttribute(a.nodeName));
						}
						catch (err) {
							// ignore this error... doesn't seem to make a difference
						}
					}
				}
				if (deep && node.childNodes && node.childNodes.length > 0) {
					for (i = 0, il = node.childNodes.length; i < il; i++) {
						newNode.appendChild(document.importNode(node.childNodes[i], deep));
					}
				}
				return newNode;

			case document.TEXT_NODE:
			case document.CDATA_SECTION_NODE:
				return document.createTextNode(node.nodeValue);

			case document.COMMENT_NODE:
				return document.createComment(node.nodeValue);

			case document.DOCUMENT_FRAGMENT_NODE:
				docFragment = document.createDocumentFragment();

				for (i = 0, il = node.childNodes.length; i < il; ++i) {
					docFragment.appendChild(document.importNode(node.childNodes[i], deep));
				}
				return docFragment;
		}
	};
}

When I needed an importNode() shim for IE8 I found a number of useful looking resources:

• https://gist.github.com/lakenen/5165619
• http://stackoverflow.com/questions/1811116/ie-support-for-dom-importnode
• http://alistapart.com/article/crossbrowserscripting

but there were minor issues with all of them, and none of the solutions supported document fragments, which are needed to work with HTML5 templates. The polyfill above was adapted from these solutions, and seems to work for me.

I think that in line 61 you should be
var docFragment = document.createDocumentFragment();